A virus frozen in the Siberian permafrost since the Ice Age has been revived. The virus itself is harmless, but the researchers responsible warn that Global Warming could release more malign lifeforms from the frozen ground
The virus was found at the bottom of a 30m sample collected in Chukotka, East Siberia, and named Pithovirus sibericum. It follows from the discovery that the seeds of plants buried at the same time could be brought to flower.
P sibericum infects amoeba, not humans, and is huge by viral standards. It has 500 genes, while the influenza virus has just eight – proving that when it comes to making you sick, size doesn't matter. At 1.5μm wide it can be seen with an optical microscope, and is the size of small bacteria. The results were reported in PNAS.
P sibericum's large genome makes it a Megaviridae, but it differs substantially from previously known species. The paper's authors, led by husband and wife team Jean-Michel Claverie and Chantal Abergel of Aix-Marseille Université, speculate that the discovery could represent a link between previously known Megaviridae and Iridoviruses, a family of viruses that infect invertebrates and occasionally fish and reptiles. Claverie and Abergel discovered the first supersized virus in 2003 and several others since.
Pithos is the Greek word for containers used to store food and wine, whose shape the virus resembles. “We're French, so we had to put wine in the story,” Claverie told Nature. Even aside from its great age, the Pithovirus has enough unusual features to attract attention. At one end it has a honeycomb structure capping its opening. Where most viruses take over the nucleus of their host's cells to reproduce, this one uses the cytoplasm.
While having a large genome by the standards of most viruses, the Pithovirus has a third as much material as some Megaviridae, despite being even larger spatially. “That huge particle is basically empty,” says Claverie. “We thought it was a property of viruses that they pack DNA extremely tightly into the smallest particle possible, but this guy is 150 times less compacted than any bacteriophage [viruses that infect bacteria]. We don’t understand anything anymore!”
The French National Centre for Scientific Research (CNRS) warned, that the discovery, “Has important implications for public-health risks in connection with exploiting mineral or energy resources in Arctic Circle regions that are becoming more and more accessible through global warming.”
“The revival of viruses that are considered to have been eradicated, such as the smallpox virus, whose replication process is similar to that of Pithovirus, is no longer limited to science fiction,” the CNRS statement continued. “The risk that this scenario could happen in real life has to be viewed realistically.”
